Acoustat manufactures or has manufactured the following equipment (click to expand models list):Dynamic Speakers
The technology of full-range-element electrostatic loudspeakers by James Strickland, President of Acoustat Corporation. (PDF, 1.2 MB, 6 pages)
A factory tour (by Andy Szabo, March 2002)
Marco Visona (November 2000): I want to inform my friends Acoustat lovers that Acoustat is now a brand owned by a Chinese company (sigh, sigh). The Italians has went to China, after a long and terrible trip and they sold brand, technology and repairing skills. This is not necessarily a damage, maybe the Chinese will restore our beloved brand.
Malcolm Dean (November 2001): Business Credit Management UK lists a voluntary liquidation of Acoustat last year: 14/01/99, Acoustat Ltd 02.00 pm Bristol Drew Dunn replied on the above information (November 2001): The "Acoustat, Ltd" that Malcolm Dean mentioned made environmental controls for workplace acoustic management. I don't think that it's our beloved Acoustat, the speaker manufacturer.
Jim Curry (November 22, 2004): Southeastern Transformers of Miramar, FL was acquired by Galaxy Transformer in 1998, and subsequently relocated to South Jersey. Southeastern was one of the original transformer suppliers for the Acoustat product line. Today, Galaxy Transfomer & Magnetics still sells replacement transformers. Galaxy Transformers website is: www.galaxytransformers.com
James Wong (March 3, 2005) The Acoustat brand has once more emerged from its ashes. The "Acoustat, Ltd" brand is now in Chinese hands. The information is a bit sketchy as most of the site is in Chinese. More to follow!
Nemish Mehta (March 29, 2005): Acoustat is indeed in Chinese hands and is being made again. I have come across this brand recently (in China!!) and have bought some models (probably renamed from the Spectra series). Only have a feel for the lineage through several forums.
I would like to discuss with Andy Szabo et al., whether worth resurrecting. The new amps are not really great. I assumed that ESL manufacture was a high tech operation but looking at the pictures that Andy has posted, perhaps the Chinese can make high end ESL's utilising low labour costs!
Nemish Mehta (February 18, 2010): The speakers being made were not simialr to the old Spectras as far as I was able to tell. Since 2009 I have not heard from the Chinese manufacturer, possibly as there was little or no market in the UK for these products. In 2008, I closed down my importing from China. The Chinese website also does not seem to have been updated since 2008. This is a shame as I still get occasional emails from people who have the old Spectras and need repairs, refurbishment, etc. I usually point them to this forum so anybody still working with these speakers - please update with your details!
milan puncer (September 27, 2014): hello
I am looking to purchase THYRISTOR for acoustat model x servo driver amplifier.
Please somebody help.
Kind regards from MIlan
He (February 28, 2015): i own a model 3 Acoustat set of speakers that were given to me 25 years ago and have been boxed and bubble wrapped. I recently tried to hook them up to a fairly high end Sony 333es receiver (80 watts per channel) and no sound or hum. I am not sure if I need a formal power amp to power it or whether it could be 2 blown fuses together which seems unlikely. Any suggestions would be much appreciated!
Barry Wilkinson (March 2000): The financial difficulties referred to in the article below (by John Doe) took place in the early 80's . I can still remember the cover of the issue of Stereophile announcing that acoustat was returning from the dead (yes a Phoenix was on the cover) and that David Hafler had rescued them. Then later in the 80's, Hafler sold his Company (including Acoustat) to Rockford-Fosgate, but it was not in financial difficulty, at the time of sale. Hafler became a division of R-F , but under Haflers Management and when he retired Jim Strickland took over as head of the Hafler division.
John Doe (April 2000): This company was originally based in Florida in the USA. My experience with them started in 1982 when I purchased a set of their Model 2+2 speakers. At the time, Acoustats were a rather tall speaker (almost 240 cm ! ) whose design consisted of an array of stacked electrostatic panels (one above the other) in multiple groupings. For example, the 1+1s were the smallest, then came the 2+2s, 3+3s, etc.. These speakers, in my opinion, were some the best sounding speakers available at the time. However, they had a few not-so-inconsequential problems : they required amplifiers with very high current delivery capability at very low impedance (down to less than 1 ohm in some cases). They were also very inefficient (82 to 84 dB with 1w @ 1m), and tended be a bit "beamy" sounding in the upper octaves (progressive narrowing of the radiation pattern with the increase of frequency). In the late 1980s, Acoustat was experiencing serious financial difficulties and was eventually absorbed by the Rockford Fosgate Corp. (the car audio people) who also happened to own the Hafler Company. By the way, David Hafler was also the brains behind the original Dynaco company, who are back in business building reasonably good solid state and tubed home components in the USA. Rockford relocated Acoustat to their own facilities in Arizona and invested a sizable pile of money into the research and development of an entire new line of hybrid and full-range speakers, which upon introduction, became known as the Acoustat Spectra Series. These speakers did not rely on physically placing the adjacent panels at an angel to each other to rectify the narrowing of radiation in the higher frequencies, but rather achieved this remedy electrically (hence, the name Spectra). There were initially three models available:
- Spectra 11 (1 panel)
- Spectra 22 (2 panels side-by-side ; I own a pair of these)
- Spectra 33 (3 panels)
About three years later, two larger models were introduced:
- Spectra 44 (4 panels: 2 on top, 2 below)
- Spectra 66 (the "Ultimate" Acoustat) with 6 panels in the array.
Another interesting aspect of the Spectra line was that they were a Two way system, with half or more of the panels doing low frequency duty only, whereas the older Plus series was strictly full range. About a year before Rockford realized that there was no future for them in the high-end home audio field, a cosmetically updated series was made available, the 2200, 3300, 4400 and 6600, and the Spectra 11 was replaced with the Spectra 1100, which featured a built-in eight or ten inch dynamic woofer. This was not a subwoofer. Acoustat did have a line of two real subwoofer units which perfectly matched their ESL's, but were not entirely necessary. Acoustats can make bass on their own....REAL bass that you can Feel ! Rockford Fosgate also introduced a line of amplifiers under their Hafler name called the TransNova XL series. These amps were supposed to have simplified the choosing of amplification for the Acoustats because at that time, any amps which suitable to drive these speakers were extremely expensive.
The TransNovas were more stable with the very low impedance found in the Ells, and had a large current output capability and huge heatsinks. Personally, I never liked the sound of these amps, and I have always used Classe electronics to drive my speakers. I have found them to be very musical and extremely durable and reliable. I have also used Sonic Frontiers amps with my Acoustats. My choice of amplification is also tempered by the fact that I live in Canada, and non-Canadian components such as Krell or Mark Levinson are much less affordable here. As far as I can ascertain, Rockford killed the Acoustat division in 1993. In 1995 (approximately) the Acoustat name resurfaced as a division of the Italian firm Audio Physic. They are building electrostatic speakers in Italy which are based on the Spectra design principals. However, when I contacted them, I was told in no uncertain terms that they had NO intentions of ever exporting these interesting speakers to North America. They were intended for sale in certain parts of Europe ONLY! Audio Physic is selling only their dynamic speaker line outside of Europe.
Mike Savuto (July 2000): The first model manufactured by Acoustat was the Acoustat X, made from late 1976 until early 1980. The "X" designation was actually stylized from the electrical representation of an electrostatic speaker design as shown in the manuals. This is the floor standing speaker with the panels in a Walnut trimmed cabinet with the Servo-Charged amplifiers in the bottom of the cabinet and the removable "pegboard" back. They retailed for $1995.
The Monitor 4 came out in late 1978 or early 1979 at about $2995. Acoustat made it available as a DIY kit to upgrade Acoustat X's as well at a very reasonable price, $750. The original Monitor 4 was the "Wing" design with solid Mahogany (black grill cloth) or Oak (white grill cloth) top and bottom caps on a separate base as shown in the pictures on the ESL website.
In 1980 the Monitor 4 cosmetics were changed so that the "Wing" extended to the floor, doing away with the separate base. It was now a monolith design. This is the design shown in the Owners and Service Manual also made available during that time.
The Model X was superceded during that same time by a Monitor 3 with the monolith cosmetics similar to that of the revised Monitor 4. Also in 1980 the first Magnetic-Kinetic (MK-121) interface was introduced. For a time the Monitor 3 and 4 were available with the Servo-Charged amplifiers and the same panel configuration with the MK-121 interface designated as "Model 3 or 4".
In December of 1981 the last Servo-Charged amplifiers were built. All subsequent models utilized the MK-121, and later the Spectra, interface and amplifiers of the owners choice. One source of confusion is that every Servo-Charged amplifier, until very close to the end of production, had "Acoustat Model X" on the serial number sticker. The amplifiers were all the same basic design for each model. The model designation of the speaker array itself was never indicated on the speaker "cabinet" or the Servo-Charged amplifiers. During the time when the MK-121 was being introduced, and the Servo-Charged Amplifiers were being phased out, an excellent article was produced by a short lived audiophile publication, whose name escapes me, that tested and compared the sonics of two designs and officially announced the passing of the Servo-Charged amplifiers. The King was dead.
Hafler home page (January 2001): James C. Strickland, Vice President - Engineering, received his degree in 1963 from the university of Miami. Jim taught physics and mathematics from 1963-1969, while also pursuing development of electrostatic loudspeakers. Jim started his electronic design career with MCI-Sony in 1969. Shortly after becoming Vice President of Engineering there, he developed both analog and digital circuitry for professional multi-track tape recording machines. His work on the digital Automatic Locator and the digital and analog controls of the JH-100 tape decks allowed this series to become the most widely used multi-track machine in the world. In 1984, Acoustat was merged into Hafler, with Jim remaining as Chief Engineer for Acoustat. He developed the SPECTRA drive principle for electrostatic loudspeakers and the IRIS system of digital-analog remote control - ultimately yielding another patent for Rockford, which acquired Hafler in 1987.
Phil Porcari (Februari 2002): As an owner of Acoustat speakers I can tell you that they are sadly no longer being manufactured. The last company I know of who made them was the Rockford Corp. in Tucson.
A Historical Overview (Andy Szabo, march 2002)
The Robot Underground (November 5, 2004): I worked for a summer for Lightning Audio. At that time the accessories brand was being absorbed by Rockford Corp and I got a tour of the RF facilities. One thing that was mentioned was that when RF bought Acoustat, the guy that wrote the contract forgot to place reponsibility for repair on Acoutat speakers to the Italian company that had bought the brand. When I called for info on my Spectra 11 power supplies, the tech confirmed what I had heard. That contract guy was so fired. RF is still responible for build on speakers that had a lifetime warranty. RF tech support: 800-669-9899.
Refurbishing & modifications
Brian Wallen (August 6, 2005): Roy Esposito at Sounds Like New does restoration work, specializing on Acoustat products, but also working on other brands. Most of us are impressed with products like those from Marantz and Macintosh that seem to be so well built that they run forever. These people seem to have cared that a product that bore their name was of very high quality. Roy's service seems to be in this mold. I feel especially comfortable sending him my Acoustat equipment, since he was part of Acoustat's engineering staff.
An example of Roy's service: Maybe five years ago, I sent him an Acoustat Trans-Nova amplifier, which he rebuilt. I had replaced it with a more powerful amp and hadn't used it in a year or so. When I connected it, I found one channel was dead. I sent a note to Roy and got an immediate response, walking me through diagnostic steps I could take to identify the problem. Fortunately, it was just a blown fuse that looked ok.
Andy Szabo's Technical Bulletins
Acoustat owners are among the most lucky hifi enthusiast in the world. Who else can rely on having a former Acoustat engineer, designer and general manager like Andy Szabo and an Acoustat refurbishing expert like Mike Savuto to keep their beloved speakers alive? Andy has been answering questions of Acoustat owners for over four years now and since a year and a half Mike has joined forces to answer the questions for the oldest models.
Andy Szabo was an engineer and general manager for Acoustat, from 1985 (when acquired by Hafler), to the end of US production. He is available to answer questions, both technical and historical. His product knowledge is most complete for models produced after 1985, but he knows a good amount about older models, too. Mike Savuto's will answer the questions regarding the Model X, Monitor 3 and Monitor 4. His company Analogue Associates can refurbish and/or upgrade them.
All questions will be answered as promptly as possible. Before posting a new question, please check the section corresponding to your speaker model number. Your question may have already been answered. Also check the sections for similar models under the same main heading (for example, if you have a Model 2+2, check all the sections that use the same interface. You can ask your questions directly on the concerning models pages and we will try to answer them within a reasonable time.
Rather than answering frequently asked questions directly, Andy has chosen to write some general documents that will hopefully answer these questions, and provide much needed information to others. Many commonly asked questions are answered there:
General Model Information (by Andy Szabo)
Grille cloth removal, cleaning and replacement (by Andy Szabo)
Medallion transformer Modification (by Andy Szabo)
MK-121 Interface Versions (by Andy Szabo)
MK-121-X Low Frequency Transformer Tap (by Andy Szabo)
Popping Panels (by Andy Szabo)
Spectra Sectoring and Color Codes (by Andy Szabo)
Spectra series, Bass Equalization - transformer taps (by Andy Szabo)
Ultrasonic Bias Power Supply - When, Why & How, Wall transformers and Adjustment (by Andy Szabo)
Ultrasonic Bias Power Supply -Update Acoustat Spectra series (by Andy Szabo)
Ted Nugent vs. Spectra 1100 (by Andy Szabo)
Rehabilitation of a Spectra 4400 (november 2005 by Andy Szabo)
General Notes (by Bear, March 2002)
Notes on Acoustat (by Sean Bowes)
Tweak for electrostatic speaker owners (by Bob Blase)
The Medallion modification (by Kevin Ferry)
C-Modification, MK-121 Series (by Andy Szabo)
MK-121-2(A) Medallion "C" Modification Parts and upgrade wiring from the older to the newer medallion upgrade. It does not contain the schematic of the older 121-2A transformers.
Gary L. Thomas (January 10, 2012): I need some info on the power supply-especially the tapped wirewound resistor
Roy A. Esposito (September 6, 2013): Hello Friends --
This is just to let you know that my email contact
has recently changed. It seems AT&T/Yahoo could no
longer support my very old prodigy.net email address.
For those of you requiring fantastic restorations
and upgrading of Acoustat MK and Spectra Interfaces
and Acoustat Power Amplifiers and Preamplifiers
my new email address is
(please notice the dots/periods between the words)
Email is the preferred method for initial contact with me
for Acoustat Service and questions.
Thank you for your continued friendship, kind comments and reviews,
and support of my work.
All the Best,
Roy A. Esposito
Izzy Wizzy Audio Nice project on metal frames for 1+1 and other Acoustat stuff Quad
Forum topics on Acoustat
The following topics regarding Acoustat in general can be found in the forums. Topics about specific models can be found on the model pages. If you want to start a new topic, click here.